"Genie" Was Kept Isolated by Her Parents and Never Spoken

"Genie" was kept isolated by her parents and never spoken to until she was 13 years old. A problem with generalizing from her experiences to draw conclusions about the language skills of children in general is that:

A) her situation was more of a correlational than experimental design.
B) researchers only discovered Genie when she was 13, well after her language skills should have developed.
C) it is difficult to create an observational protocol that would suit her case.
D) she was not only deprived of language, but also experienced an extremely harsh and unusual childhood.